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Weighing in at 20 pounds and measuring four feet long, Granddad is believed to be the oldest fish in captivity at any public aquarium or zoo in the world. The Shedd estimates he’s at least a century old and that an “excess of 100 million visitors” have passed through the aquarium since his arrival.

The fish came to Chicago from Sydney’s Taronga Zoo at the behest of Walter H. Chute, then-director of the Shedd, who said the aquarium was “particularly desirous of securing one or two specimens” of the Australian lungfish for the Century of Progress Exposition, Chicago’s second world’s fair, held in 1933.

Australian lungfish can live a long time, but even Granddad is pushing the upper end of those limits. And he wasn’t always referred to as an old man. In 1994, the fish was joined at the Shedd by five younger Australian lungfish donated by the University of Queensland and Australia’s Sea World park. Before the youngsters’ arrival, he was called Methuselah, after a character from the Hebrew Bible who lived for 969 years.

The Shedd's senior aquarist Michael Masellis said Granddad's longevity is due to "good care, a good diet and stable conditions." (Shedd Aquarium)

Michael Masellis, senior aquarist at the Shedd and Granddad’s primary caretaker, admits the old lungfish isn’t very animated; in fact, he affectionately likens Granddad to a “fallen log.”

“That’s their strategy in the wild, so that’s what he does here at the Shedd,” Masellis said. “The most excited he gets is on earthworm Wednesdays, when we throw a couple handfuls of earthworms in there.”

The fish also show curiosity by bumping into the aquarist while he’s cleaning their exhibit’s windows.

“They’re super slimy, which I was pretty surprised by when I started working with them,” Masellis said. “All fish have a mucous layer that protects them from disease, but lungfish seem to be slimier than usual.”

This vintage photo of Granddad was taken in the 1930s, according to the Shedd. (Shedd Aquarium)
Unfortunately, Granddad and his mate from that 1933 journey to Chicago never successfully bred – his mate passed away in 1980.

Granddad isn’t just an elderly fish – he’s prehistoric. Australian lungfish are considered “living fossils” because fossil records indicate the species has changed very little in 150 million years.

There’s evidence Australian lungfish lived 380 million years ago, dating back to the evolution of tetrapods, land-living vertebrates, when pre-historic fish began crawling out of the water, kickstarting the evolution of four-limbed species.

In fact, Granddad’s physical anatomy illustrates his point at an evolutionary crossroads. Like other fish, Granddad obtains oxygen underwater through his gills, but as his name suggests, he also possesses a single lung from which to breathe air above water. The fish can even survive on land for several days, although they'll die if they dry out.

This month marks the 83rd anniversary of Granddad's arrival at the Shedd. Visitors can see him and his younger lungfish peers, which are about 30 years old, at the aquarium's Waters of the World exhibit.

April 25: After Lurie Children’s Hospital of Chicago patients, families, staff and volunteers took part in a voting contest last week, the 10-month-old penguin previously known as Chick No. 23 is now called Diego.

February 25: The Chicago River is far from America's cleanest waterway. But a few anglers are trying their luck as its ecosystem improves. Captain Tim Frey took us for a winter fishing trip on the river.